Two of your posts were for the same unregistered user, who was going around spamming a giant wall of text. I deleted the user, which deleted the posts and cleared the flags on those posts automatically. I assumed the flags were automatically dismissed as valid, but this appears this might not have been the case.
However, one possible way to lose flag weight without realizing it (or having moderators know what happened) is to lose it on comment flags. When you flag a comment, moderators have four options:
- Delete the comment outright
- Edit the comment to remove the offending bits
- Dismiss the comment
- Take no action and/or leave another comment addressing the first commenter (e.g. "Be nice")
Only the first two options awards an increase of 5 flag weight outright. The third will decrease your flag weight automatically, and the last will decrease your flag weight if four other people don't also flag the comment (a common occurrence, especially if a moderator steps in via comments).
And, unlike flagged posts, these won't show up on your flag weight audit. You'll just see the change in flag weight.
Discussion on Meta Stack Overflow: Can a flag that attracts moderator action be treated as invalid?
But as Chris said, please don't put too much weight into flag...weight, especially on Programmers.SE. We don't get so many flags per day that having a low flag weight actually matters: we act on everything, even if that action is to take no action right away.